A fixing device has a problem that a variation of a temperature of a heating member is large when heat capacity of the heating member is small. Therefore, there is a fixing device configured to prevent the variation of the temperature of the fixing device by using a pressurizing member having large heat capacity. However, when the heat capacity of the pressurizing member is large, warm-up takes time. Also, there is a multifunction printer or the like having a plurality of modes, in which a heating temperature of the heating member is different. For example, there is a multifunction printer using decolorizing toner. Such a multifunction printer switches the temperature of the heating member between a first temperature at which the decolorizing toner is fixed and another temperature at which the decolorizing toner is decolorized at a temperature higher than the fixing temperature. When the heat capacity of the pressurizing member is increased in such a multifunction printer, it takes time for the temperature to decrease from the decolorizing temperature to the fixing temperature, and thus the switching undesirably takes too much time.